<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<meta name="viewport" content="width=device-width, initial-scale=1">
	<title></title>
</head>
<body>

</body>
</html>

<!--<script type="text/javascript">
	var a =10;
	var b =NaN;//不是存数字字符串，或是undefined不能进行字符运算
	var c =30;

	document.write("hello"+undefined);//

</script>
-->

<!--<script type="text/javascript">

	alert(200-"10");
	alert(200*"10");
	alert(200/"10");
	alert("200"+"10")
	alert(200+"10")//对于+优先把加号认为是字符串的拼接

	//null转换为数字为0，undefined转换为数字为NaN

</script>
-->

 <!--<script type="text/javascript">
    var a = 5;
	alert(a++)
	++后置，先取a的值作为a++表达式的值，然后再对a进行+1

	alert(++a)
	++前置，先对a进行+1操作，再将a的值作为++a表达式的值



    var a=10

	alert(a++ + ++a + a+ ++a + a++ +a)

</script>
-->

<!--<script type="text/javascript">
	//alert(Boolenm(100))
	alert(Boolean("null"))
</script>-->

<script type="text/javascript">
	alert(Number(true))
</script>

  <script type="text/javascript">
  	var str = "110011010";
  	var a = parseInt(str,2);//转换为2进制的数
  	alert(a)
  	var b = parseInt(a,8);
  	alert(b)
  	var c = parseInt(a,16);
  	alert(c)
  </script>